1. Related Patents
The present application is an improvement of the invention taught by the applicant's application Ser. No. 292,224 filed Dec. 30, 1988 now U.S. Pat. No. 4,872,453.
2. Field of the Invention
The present invention is generally related to snorkels used by skin divers. More particularly, this invention is concerned with purging water from a flooded snorkel.
3. Description of the Prior Art
Skin divers use the snorkel as a means to breathe while swimming face down on the water surface. The snorkel functions as a conduit between the diver's mouth and the overhead air. One end of the snorkel conduit is open and typically extends a short distance above the water surface. Occasionally, due to swimming movements or wave action, small amounts of water flow into the open end of the snorkel and partially flood the conduit. Also, water will flood the snorkel when the diver swims or dives below the water surface. An experienced skin diver can sense when water enters the snorkel and responds by immediately stopping inhalation. Respiration is resumed after the snorkel has been purged of water.
A diver returning to the surface after an underwater swim will be starved for air. Upon reaching the surface and after the snorkel is purged, the first breaths through the snorkel are typically fast and deep. The diving community considers snorkels which provide air with little respiratory resistance to be very desirable. Accordingly, to ease respiration, the state of the art sizes the inside cross-sectional area of the conduit to provide respiratory flow with as little resistance as possible. Equally important for the state of the art, the conduit must be free of any obstructions or flow restricting structures which hinder respiratory flow.
In addition, there are other considerations of the art concerning the size of the conduit. Overly large conduits add significantly to the bulk of the snorkel which makes the snorkel undesirably cumbersome and difficult to swim with. And as will be discussed shortly, water cannot be easily purged from overly large conduits.
Inexperienced skin divers find occasional flooding especially troublesome because, undetected, water can be inhaled resulting in coughing and extreme discomfort. Consequently, several configurations have been proposed to restrict or block the normally open end of the snorkel and thereby prevent water from entering.
U.S. Pat. No. 2,317,236 entitled Breathing Apparatus for Swimmers, issued to C. H. Wilen, et al, on Apr. 20, 1943, teaches a valve with a buoyant ball arranged to block the above water end of the snorkel whenever water starts to enter. Such valves are bulky, often fail to seal and, also, significantly increase respiratory effort. Although once popular, such devices are now considered unreliable and obsolete.
A recent invention functionally similar to the snorkel of Wilen, U.S. Pat. No. 5,117,817 entitled Vertical Co-Axial Multi-Tubular Diving Snorkel, issued to Hsin-Nan Lin on Jun. 2, 1992 teaches an annular float arrangement which blocks the above water end of the snorkel whenever water starts to enter. To assist in purging, the Lin snorkel also incorporates a secondary purge tube within the breathing conduit. The Hsin-Nan Lin snorkel suffers from the same problems as the Wilen snorkel.
U.S. Pat. No. 4,071,024 entitled Snorkel, issued to Max A. Blanc on Jan. 31, 1978, teaches an air entrapping cap which is mounted on the above water opening of the snorkel. A tortuous passage in the cap retards water flow into the snorkel. Although such a cap is somewhat effective in blocking the occasional flow of surface water into the snorkel, it also retards expulsion of water which enters the snorkel during a dive or swim below the water surface. The significant increase in respiratory and purging effort limits its utility and subsequent popularity.
Similar to Blanc, U.S. Pat. No. 5,199,422 entitled Modular Snorkel, issued to Stan Rasocha on Apr. 6, 1993, teaches an exhaust valve mounted on a cap which covers the upper end of the snorkel. The cap restricts the entry of splashed water into the snorkel. The exhaust valve on the cap permits the expulsion of water from within the snorkel during a purging exhalation. Rasocha's snorkel increases respiratory effort and does not noticeably reduce purging effort.
The open snorkel conduit will be completely flooded with water when a skin diver returns to the surface after swimming or diving underwater. The open end of the snorkel is above the water when the skin diver swims face down on the water surface. With the open end of the snorkel above the water, the conduit is purged for respiration by exhaling an explosive blast of air into the mouthpiece.
Surface tension forms the purging blast of air into a bubble which spans the cross section of the conduit. Pressure within the bubble expands the bubble toward the open end of the snorkel conduit. As the leading surface of the bubble moves away from the mouthpiece, the bulk of the water within the conduit is pushed ahead of the bubble and out the open end.
However, the purging bubble of air will slip past water which adheres to the inside surface of the conduit. Consequently, the size and shape of the cross-section of the snorkel conduit greatly affects the purging action of the expanding bubble. For example, if the inside cross-section is overly large, the expanding bubble will tend to concentrate more in the center of the conduit cross-section and, consequently, substantially more water will adhere to the conduit wall. Also, if the conduit cross-section shape is other than circular, e.g. elliptical or rectangular, the circular shape of the expanding bubble will tend to miss water outside the circular center of the conduit. In addition, structures within the conduit, or attached to the open end of the conduit, not only restrict respiration but interfere with the purging flow as well. Such structures are customarily avoided by the art.
In general, snorkels having larger cross-sections breath noticeably easier but purge poorly; conversely, snorkels having smaller cross-sections breath poorly but purge more completely. And snorkels having circular cross-sections breath and purge easier, but are not as streamlined for swimming as, for example, an elliptical cross-section. Choice of the size and shape of the snorkel conduit by the art is a compromise which considers the various factors. Based on years of experience by those who manufacture and sell snorkel equipment, and tested by the popular acceptance of the diving community, the optimum snorkel configuration has an open, unobstructed circular cross-section with an inside diameter in the range from 19 mm to 22 mm (3/4 inch to 7/8 inch). Deviations from this norm have limited success within the diving community.
After the purging air bubble is spent, residual water will flow down the inside surface toward the mouthpiece. Also, water which splashes into the open end of the snorkel conduit due to swimming movements or wave action will typically strike and adhere to the inside surface of the conduit and thereafter flow toward the mouthpiece. Water accumulates at the lowermost portion of the snorkel conduit, typically adjacent the mouthpiece, and soon obstructs the conduit. Unless the conduit is completely blocked, a slow and cautious inhalation is possible after which another purging exhalation can be made.
The respiratory effort needed to purge a snorkel is significant. Many skin divers lack the respiratory strength needed to completely purge a flooded snorkel with a single exhalation, and must repeat the purging procedure several times. Also, water will sometimes enter the snorkel just as the diver has completed an exhalation, leaving very little air in the lungs to satisfactorily complete a purge. Consequently, a means which decreases the respiratory effort and the amount of air required to purge a snorkel will be very beneficial.
A popular solution places an externally directed purge valve in the wall of the snorkel conduit at a location near the snorkel mouthpiece. Water in the flooded conduit which extends above the ambient water surface will drain through the purge valve. Because the total volume of water in the flooded snorkel is reduced by water flow through the purge valve, the respiratory effort required to purge the remaining water is also reduced.
Unfortunately, a purge valve also provides an alternate path for forcefully exhaled air. A purge valve located close to the mouthpiece will quickly and wastefully dissipate the explosive blast of purging air. One solution to this problem places the purge valve at a location approximately midway between the mouth opening and the open end of the snorkel conduit.
At mid-length of the snorkel conduit, the purge valve will be close to the ambient water surface when the skin diver is swimming face down on the water surface. At such a location, the purge valve will drain that portion of the snorkel conduit which extends above the water surface, but will not initially interfere with the purging blast of air. Even at this location, the purge valve will dissipate the forcefully exhaled air and the amount of residual water adhering to the inner surface of the conduit between the purge valve and the open end will be substantial. The residual water subsequently accumulates at the lowermost portion of the snorkel conduit and obstructs the conduit. Consequently, the purge valve by itself, even when located mid-length of the snorkel conduit, is of limited benefit.
U.S. Pat. No. 4,278,080 entitled Diving Snorkel, issued to Joseph N. Schuch on Jul. 14, 1981, teaches a purge valve located at the bottom of a branch conduit which joins the snorkel conduit at a location approximately midway between the mouthpiece and the open end. The purge valve drains the snorkel conduit until the water level within the conduit matches the ambient water level. Part of the purging air will divert into the branch conduit and force water within the branch conduit out the purge valve. Schuch teaches that the branch conduit must have sufficient length to provide the transient resistance necessary to allow purging of the snorkel conduit before the purging air reaches and is dissipated by the purge valve.
Water within the snorkel conduit of Schuch is pushed out the open end before the purging air clears the branch conduit of water and reaches the purge valve. Nevertheless, diverting part of the purging bubble of air into a branch conduit abates the driving pressure within the purging bubble and allows significant residual water to adhere to the upper portion of the snorkel conduit. Consequently, although the snorkel configuration of Schuch somewhat reduces the effort required to purge a flooded snorkel, it does not decrease the amount of purging air required, and it does not reduce residual water which adheres to the snorkel conduit wall and soon flows down the wall to obstruct the snorkel conduit near the mouthpiece. Also, the branch conduit adds significantly to the size of the snorkel, making the snorkel unwieldy in use.
As another approach, U.S. Pat. No. 5,143,059 entitled Water Trap for a Snorkel, issued to John Delphia on Sep. 1, 1992, teaches a water trap adjacent a purge valve located approximately mid-length on the snorkel. Water flowing within the snorkel is deflected and retained until discharged through the exhaust valve. The trap means of Delphia is a complex combination of baffles, lips and openings which inherently restrict respiratory flow and require relatively complex tooling for manufacturing.
Most of the attempts by the prior art to improve the snorkel have resulted in configurations which in one way or the other obstruct or restrict respiratory flow. As a result, these various configurations have experienced little or no success in the marketplace. In view of these foregoing factors, conditions and problems which are characteristic of the prior art, an improved snorkel was taught by the applicant's application Ser. No. 292,224 filed Dec. 30, 1988 now U.S. Pat. No. 4,872,453 which issued Oct. 10, 1989. The improved snorkel features a chamber that intersects the conduit at a location that is at approximately mid-length. The chamber houses a float member. When the snorkel is free of water, the float member resides in the chamber and does not interfere with respiratory flow. When water fills the snorkel, the float member is buoyed out of the chamber into the conduit and blocks upward flow therein. The flooded snorkel is purged by exhaling into the mouthpiece. Because the float member blocks upward flow when the conduit is flooded, the upwardly expanding exhaled air is trapped beneath the float member. The trapped air displaces the water in the conduit, forcing the water down and out the purge valve. As a consequence, the effort and amount of air required to purge the Christianson snorkel are significantly reduced.
U.S. Pat. No. 4,872,453 satisfied the need for a snorkel with an unobstructed respiratory flow path from which water could be purged with a minimum of respiratory effort and without a wasteful loss of purging air. However, the protruding chamber proved to cause undesirable turbulence during swimming. The intersecting chamber also required relatively complicated and expensive tooling for fabrication. Furthermore, a second purge valve was found to be needed to eliminate water trapped in the snorkel conduit above the chamber intersection. These problems discouraged the practical application of the invention.
The present application improves on the invention taught by U.S. Pat. No. 4,872,453. The improvement eliminates the need for an intersecting chamber located at approximately mid-length of the snorkel tube, yet maintains an open and unobstructed respiratory path when the snorkel is not flooded with water. As a result, the instant invention can be manufactured with relatively simple and inexpensive tooling, swimming turbulence does not occur, and a second purge valve is not needed.